Positive displacement superchargers of the Roots or screw type may be used in automotive engine applications to increase the cylinder air charge and, thus, provide for increased engine output. The rotors of a supercharger may be formed with helical lobes that provide for axial airflow from an inlet to an outlet of a supercharger housing. The inlet and the outlet of the supercharger housing may be configured to improve efficiency and reduce noise generated by the supercharger.
Engine intake air enters the supercharger at near-atmospheric pressure. The engine intake air directly upstream or downstream of the supercharger may be subject to pressure pulsations inherent to the operation of the supercharger. As a result, sound attenuation devices such as Helmholtz resonators and quarter wave chambers are often installed in the air intake system of the engine, upstream or downstream of the supercharger, in order to reduce resultant noise generated by the pressure pulsations. The addition of the aforementioned sound attenuation devices has proven to be sub-optimal in that they can be costly, they require space that is often at a premium in automotive under-hood applications, and they may not necessarily be locatable as close to the source of noise as is desired for effective noise reduction.
Accordingly, it is desirable to provide a noise attenuation device for a supercharger that is cost effective and may be located in close proximity to the location of noise producing pressure pulsations.